Softening compositions including alkanolamino functional siloxanes
BACKGROUND OF THE INVENTION 
     This invention relates to a fabric softening composition which includes a mixture of an alkanolamino functional siloxane and at least one surfactant which is anionic. The invention is also directed to detergent laundering products containing the fabric softening composition. 
     Solid detergent formulations are sold in powder or granular form. A disadvantage of solid detergents is that, on account of the hygroscopic nature of individual raw materials of the formulation, the solid detergent shows a pronounced tendency towards caking or clumping in the presence of small quantities of moisture. This does not make the detergent unusable, however, it results in clumping of caking of the individual components of the detergent in the presence of moisture. Thus, the appearance of the detergent in most cases is diminished. As a result, there has been a desire to develop liquid detergent compositions for convenience in lieu of conventionally formulated solid detergent compositions. The liquid detergent allows for use of lower washing temperatures inclusive of cold water laundering. Granular detergents have not fully adapted to such variations because of weaknesses in respect of dissolving speed, insolubility, and cleaning efficiency. Due to such problems of caking and the slowness of solid and granular detergents to dissolve, trends in detergent manufacture have leaned toward the liquid detergent. Such detergents usually include one or more anionic, nonionic, and cationic organic surfactants, water, brightening agents, hydrotropes, enzymes, soil suspending agents, bleaches, pH modifiers, and solvents. It is not uncommon to also include antifoam formulations as a part of the detergent package. Such systems may be built or free of builders. 
     A fabric softener, on the other hand, often contains a dilute solution or dispersion of a quaternary ammonium organic derivative used to treat fabrics in the final rinse cycle of a laundering process in order to make the fabrics feel softer. In addition to softness, fabric softeners are known to also provide static control. Because of the affinity of quaternary ammonium compounds for negatively charged surfaces, their single largest market has been as fabric softeners. Commercial fabric softeners generally include about a four to eight percent dispersion of quaternary ammonium compound which is added to the rinse cycle of the washing process. In some cases, a fatty acid stearate is added to modify the handle. The quaternary ammonium compound can also be applied to a nonwoven sheet or a polyurethane foam which is added with wet clothes in a dryer. Such sheets contain a fatty amine or a fatty acid ester which allows the quaternary ammonium compound to transfer from the sheet to the clothes in the dryer during the drying cycle. Recently, there have been devised combined detergent and softener formulations which allow introduction of all additives in the wash cycle. 
     A basic distinction should be drawn between a rinse cycle softener and a wash cycle softener. As noted hereinabove, the rinse cycle fabric softener is a liquid dispersion of a quaternary ammonium compound which is added separately to the rinse liquor during the rinse cycle of the laundering device. A wash cycle fabric softener, in contrast, typically contains the quaternary ammonium compound which is mixed in with the laundry detergent and added to the wash liquor by the homemaker before initiation of the wash cycle of the fabric laundering device. 
     Quaternary ammonium functional siloxanes are not new in the art. For example, in United Kingdom Pat. No. 1,549,180, published July 25, 1979, there is described certain fabric conditioning compounds which are dialkylquaternary ammonium terminated linear polydimethylsiloxanes. The compounds of the present invention, in contrast, are alkanolamino functional polydimethylsiloxanes as well as the monoquaternary ammonium functional derivatives thereof. The compounds also are trialkylsiloxy terminated rather than dialkylquaternary ammonium terminated as the materials in the &#39;180 patent. United Kingdom Pat. No. 1,006,729, published Oct. 6, 1965, is directed to certain surfactants which are trialkyl mono(polysiloxy) ammonium chlorides. However, the compounds of the present invention possess a softening function beyond the capabilities of the compounds of the &#39;729 British Patent. Thus, it should be apparent that the present invention includes new and novel compositions of matter and uses thereof not previously known in the prior art. 
     SUMMARY OF THE INVENTION 
     This invention relates to alkanolamino functional polydimethylsiloxanes and including certain of the monoquaternary ammonium functional derivatives thereof. The invention is also directed to a fabric softening composition which is a mixture that includes at least one surfactant which is anionic and a silicone compound which is an alkanolamino functional polydimethylsiloxane including monoquaternary ammonium functional derivatives thereof. The softening composition is adapted to be employed as a rinse cycle additive in the rinse phase of the washing machine cycle, or the softening composition can be employed as an additive in a laundry detergent. 
     These and other features, objects, and advantages of the herein described present invention will become more readily apparent when considered in light of the detailed description of the invention which follows. 
     DETAILED DESCRIPTION OF THE INVENTION 
     Ammonium compounds in which all of the hydrogen atoms on nitrogen have been substituted by alkyl groups are called quaternary ammonium salts. These compounds may be represented in a general sense by the formula: ##STR1## 
     The nitrogen atom includes four covalently bonded substituents that provide a cationic charge. The R groups can be any organic substituent that provides for a carbon and nitrogen bond with similar and dissimilar R groups. The counterion X is typically halogen or an alkyl sulfate. Use of quaternary ammonium compounds is based on the hydrophilic portion of the molecule which bears a positive charge. Since most surfaces are negatively charged, solutions of these cationic surface active agents are readily adsorbed to the negatively charged surface. The derivative compounds of this invention are of the foregoing type. 
     The alkanolamino functional polydimethylsiloxanes of the present invention including the monoquaternary ammonium functional derivatives thereof are exemplified by the following formulas: 
     
         (R.sub.3 SiO).sub.2 SiR--(CHR&#39;).sub.a N.sup.+ R&#39;.sub.b R&#34;.sub.3-b X.sup.- 
    
     
         and 
    
     
         (R.sub.3 SiO).sub.2 SiR--(CHR&#39;).sub.a NR&#39;.sub.b R&#34;.sub.2-b 
    
     wherein 
     R is an alkyl radical having one to six carbon atoms; 
     R&#39; is selected from the group consisting of hydrogen, alkyl and aryl radicals having one to eighteen carbon atoms; 
     R&#34; is (CHR&#39;)OH; 
     X is chloride, bromide, iodide, nitrate, or RSO4 -  ; 
     a is an integer having a value of one to ten; and 
     b is an integer having a value of one or two. 
     Some of the specific species of compounds which are comprehended within the scope of the above generic formula are: 
     
         (Me.sub.3 SiO).sub.2 SiMe--(CH.sub.2).sub.3 NMe(CH.sub.2).sub.2 OH(I) 
    
     
         (Me.sub.3 SiO).sub.2 SiMe--(CH.sub.2).sub.3 N.sup.+ Me.sub.2 (CH.sub.2).sub.2 OHI.sup.-                                (II) 
    
     
         (Me.sub.3 SiO).sub.2 SiMe--(CH.sub.2).sub.3 N.sup.+ Me.sub.2 (CH.sub.2).sub.2 OCHl.sup.-                               (III). 
    
     These compouds are referred to hereinafter and in the Tables with reference to Roman numerals (I)-(III) which accompany the individual compounds as set forth above. Compound (I) is an alkanolamino functional polydimethylsiloxane, whereas Compounds (II) and (III) are the monoquaternary ammonium functional derivatives of the precursor Compound (I). 
     There is also disclosed herein certain dialkyl di(polysiloxy) ammonium chlorides which are included for comparative purposes. These comparative silicones are illustrated by the formula: 
     
         [(R.sub.3 SiO).sub.2 --SiR--(CHR&#39;).sub.a ].sub.b N.sup.+ R&#34;.sub.4-b X.sup.- 
    
     wherein R is an alkyl radical having one to six carbon atoms; R&#39; is an alkyl or aryl radical having one to eighteen carbon atoms; R&#34; is hydrogen or R&#39;; X is chloride, bromide, iodide, nitrate, or RSO 4   -  ; a is an integer having a value from one to ten; and b is an integer having a value of two or three. These comparative quaternary ammonium functional siloxanes are monoquaternary ammonium functional polydimethylsiloxanes, and are trialkylsiloxy terminated. The comparative silicone compounds can also be described as dialkyl di(polysiloxy) ammonium chlorides when the integer a is two, as well as some species of which are monoalkyl tri(polysiloxy) ammonium chlorides when the integer a is three. The dialkyl di(polysiloxy) ammonium chloride species is preferred, and especially the particular compound [(Me 3  SiO) 2  SiMe(CH 2 ) 3  ] 2  N +  Me 2  I -  wherein Me is methyl. 
     As is well known, water has a surface tension of approximately seventy-two dynes per centimeter. It has been found that solutions containing as little as 0.001 percent by weight of the compounds of the present invention possess a surface tension of about sixty dynes per centimeter, and those containing about one percent by weight have a surface tension of the order of about twenty dynes per centimeter. The compounds of the present invention can be used as additives in liquid detergents, cleaners, and automatic dishwashing detergents, and find application as ingredients in powdered detergents for fabric washing machines. These compounds can also be employed as additives in wash cycle softeners and as ingredients in rinse cycle softeners. In addition, the compounds have utility as antistatic agents, particularly in wash cycle laundry detergent formulations. The softening effects achieved by the addition of the compounds of the present invention can be enhanced by mixing the compounds with one or more anionic surfactants such as linear alkylbenzene sulfonates, and the compounds may be employed at much lower use levels in comparison to conventional commercial organic based fabric softeners. Reductions as much as fifty to seventy-five percent is not uncommon with the siloxanes of the present invention. 
     The alkanolamino functional polydimethylsiloxanes of the present invention including the monoquaternary ammonium functional derivatives thereof may be prepared in accordance with the following reaction sequence: ##STR2## wherein X is Cl, Br, I, or MeSo 4 . 
     With regard to the comparative silicones, these cationic silicone surfactants are prepared with two instead of one siloxane group attached to a quaternary ammonium functional nitrogen atom. This is accomplished by the following series of steps: ##STR3## where X is Cl, ,Br, I, or MeSO 4 . 
     The compounds are crystalline solids which have varying melting points and solubilities in water. They can function as potent surfactants, reducing the surface tension of water from 72 to 21 dyne/cm. They also adsorb very efficiently on negatively charged surfaces such as fabrics, skin, and hair. This adsorption allows for a conditioning or softening effect. 
    
    
     The following example is illustrative of a method for the preparation of the comparative silicone compound [(Me 3  SiO) 2  SiMe(CH 2 ) 3  ] 2  N +  Me 2  I -  wherein Me is methyl. 
     EXAMPLE I 
     Three hundred grams of the amine [(Me 3  SiO) 2  Si(Me)--(CH 2 ) 3  ] 2  NMe was dissolved in six hundred grams of hexane under nitrogen gas in a two liter flask and heated to reflux. Seventy grams of MeI in fifty grams of hexane was added dropwise to the flask. The product precipitated rapidly. At the conclusion of the dropwise addition, heating of the flask was continued at sixty degrees Centigrade for two hours. The material in the flask was filtered to isolate the crystalline product. One part of the product was mixed with five parts of hexane and the mixture was allowed to sit for about four days in order to leach out any impurities. This mixture was filtered, washed with hexane, and dried under vacuum. The product was characterized by proton nuclear magnetic resonance (NMR) and infrared spectroscopy. The product was identified as the compound [(Me 3  SiO) 2  SiMe(CH 2 ) 3  ] 2  N +  Me 2  I -  wherein Me is methyl. 
     The following examples are illustrative of procedures for the preparation of the alkanolamino functional precursor Compound (I) and its derivative Compound (III). 
     EXAMPLE II 
     Preparation of (Me 3  SiO) 2  SiMe--(CH 2 ) 3  NMe(CH 2 ) 2  OH 
     Into a three neck round bottom flask equipped with a stirrer, condenser, and thermometer, was placed six grams of (Me 3  SiO) 2  SiMe--(CH 2 ) 3  Cl and 6.1 grams of NH(CH 2 ) 2  OH. The system was purged with dry nitrogen gas. The mixture was stirred at room temperature and heated to one hundred-twenty degrees Centigrade. The mixture was maintained at a temperature of 120 degrees for about 3.5 hours and separated into two layers. The mixture was maintained at 110 degrees with continuous stirring for 1.5 hours and allowed to cool to room temperature. The bottom layer was discarded and volatile materials were stripped from the upper layer at 100 degrees and 17 mm vacuum for one hour. The product was obtained at a purity of about ninety-five percent. The molecular structure of the product was confirmed by nuclear magnetic resonance and infrared spectroscopy. 
     EXAMPLE III 
     Preparation of (Me 3  SiO) 2  SiMe--(CH 2 ) 3  N +  Me 2  (CH 2 ) 2  OHCl -   
     Example II was repeated except that 100 grams of (Me 3  SiO) 2  SiMe--(CH 2 ) 3  NMe(CH 2 ) 2  OH from Example II was dissolved in 150 grams of hexane at sixty degrees Centigrade. MeCl gas was slowly bubbled into the solution over a period of one hour. The mixture was cooled and the product precipitated as a white crystalline solid. The product was recrystallized from eight degree Centigrade hexane in a purity in excess of about ninety-eight percent. 
     While the liquid detergent of the present invention may contain many of the commonly included ingredients such as surfactants, builders, enzymes and enzyme stabilizers, pH modifiers, bleach activators and bleaches, antifoams, anti-redeposition agents, chelants, soil release polymers, dye transfer protectants, zeolite dispersants, water softeners, perfumes, anti-oxidants, and fluorescent brighteners, the essential ingredients for purposes of the present invention are an anionic surfactant, a nonionic surfactant, a carrier fluid, and the softening agent. Water is a suitable carrier although other fluids such as ethanol, isopropanol, butanol, hexanol, and diethylene glycol, may be employed. 
     The ratio between the anionic surfactant and the nonionic surfactant is 4:1 to 1:4, more preferably from about one to one to about three to one. The detergent should include on a weight basis at least about 0.5-5.0 percent of the silicone fabric softening agent. The softening agent is employed in an amount of about 0.05-0.3 percent by weight based on the weight of fabrics being treated. 
     The liquid detergent contains at least one surfactant and the surfactants preferred for purposes of the present invention are the nonionic and anionic types of surfactants. In nonionic surfactants, for example, there is no charge on the molecule, and the solubilizing groups are ethylene oxide chains and hydroxyl groups. Such nonionic surfactants are compatible with ionic and amploteric surfactants, and representative of nonionic surfactants are, for example, polyoxyethylene or ethoxylate surfactants such as alcohol ethoxylates and alkylphenol ethoxylates. Carboxylic acid ester nonionic surfactants include glycerol esters, polyoxyethylene esters, anhydrosorbitol esters, ethoxylated anhydrosorbitol esters, natural fats, oils, and waxes, and ethoxylated and glycol esters of fatty acids. Carboxylic amide nonionic surfactants which may be included are diethanolamine condensates, monoalkanolamine condensates, and polyoxyethylene fatty acid amide. Representative of polyalkylene oxide block copolymer nonionic surfactants are the polyalkylene oxides derived from ethylene, propylene, butylene, styrene, and cyclohexene. Typical of the anionic surfactants that may be employed herein are salts of alkyl sulfates, salts of alkylaryl sulfates, salts of alkyl ether sulfates, salts of alkylaryl ether sulfates, and salts of alkylaryl sulfonates. Exemplary materials included are, for example, alkyl benzene sulfonates, alkyl glyceryl ether sulfonates, alkyl phenol ethylene oxide ether sulfates, esters of alpha-sulfonated fatty acids, 2-acyloxyalkane-1-sulfonic acids, olefin sulfonates, beta-alkyloxyalkane sulfonates, anionic surfactants based on higher fatty acids, and tallow range alkyl sulfates. Both categories of surfactant are well known in the art and are described in more or less detail in U.S. Pat. No. 4,075,118, issued Feb. 21, 1978, for example. 
     The following examples are set forth in order to illustrate the concepts of the present invention. 
     EXAMPLE IV 
     In accordance with the present invention, silicones are emulsified in a detergent matrix by first mixing the silicone with the acid form of an anionic surfactant such as a linear alkyl benzene sulfonic acid. The mixture of the anionic surfactant and the silicone was neutralized by the addition of a base such as sodium hydroxide in a mixture of water and ethanol. The salt of the anionic surfactant results from this neutralization. Following completion of the neutralization, the nonionic surfactant was added, together with other optional ingredients such as builders, fatty acids, cationic surfactants, and optical brighteners. The mixture was mechanically agitated in order to insure a homogeneous product. It has been found that in the event that the foregoing procedure is not followed, that the silicone ingredient is caused to separate thus forming an unstable product. This occurs, for example, by the addition of the silicone to a random mixture of various ingredients. In accordance with the present invention, the silicone must be first mixed with an anionic surfactant and neutralized prior to being added to the balance of the liquid detergent formulation in order to provide a stable end product. 
     The above procedure was followed and formulations of liquid detergent containing a silicone softening agent were prepared. In each instance there was employed thirteen weight percent of an anionic surfactant, thirteen weight percent of a nonionic surfactant, five weight percent of ethanol, two weight percent of silicone softening agent, and the balance being water. The preferred ratio between the anionic surfactant and the nonionic surfactant is 1:1 to 3:1. The anionic surfactant employed was an alkylbenzene sulfonic acid of Vista Chemical Company. The nonionic surfactant was NEODOL® 25-7, a trademark and product of Shell Chemical Company, Houston, Tex., and a linear primary alcohol. Liquid detergents were prepared containing these ingredients and including the silicone softening agents. 
     EXAMPLE V 
     Towels were prepared for treatment by removing the mill textile conditioners applied at the mill during manufacture of the towels. The process was conducted at a commercial laundromat. Bundles of 86:14 cotton polyester terry towels were washed five times with an anionic detergent containing a high level of phosphorous. Detergent remaining in the towels was removed by three final wash and rinse cycles from which detergent was omitted. Each bundle was subjected to eight complete wash and rinse cycles during the stripping process followed by a drying cycle. 
     The test used to measure softness was a panel test in which twelve to fifteen people were asked to rank several towels in order of softness. Following treatment, the towels were placed in a constant temperature and humidity room over night to equilibrate, and after which the towels were tested the next day. Dryers tend to overdry towels and provide a harsher feel than normal, and therefore all towels tested in a given panel were conditioned at the same temperature and humidity before testing. Each test included one control towel. The control towel was a towel which had not been treated by a liquid detergent containing a softening agent. The people were asked to evaluate the towels by feeling the towels and choosing the harshest towel, the softest towel and placing the remaining towels in order of increasing softness. The towels were assigned a ranking between one and six with the highest value corresponding to the softest towel. Before the test was conducted, each member of the panel was asked to wash their hands to remove any residue which might interfere with the test. During the evaluation, the panel members rewashed their hands to remove any softener buildup. Since the softeness of a towel increases with repeated handling, a new surface of each towel was exposed for each panel member, and each towel was replaced after evaluation by three people. 
     EXAMPLE VI 
     Each of the liquid laundry detergents containing a silicone softening agent as prepared in accordance with Example IV was used to treat a fabric bundle which had been conditioned in accordance with the procedure of Example V. The bundles contained six towels and weighed about 1200-1400 grams. The bundle was loaded into a washing machine and about one hundred grams of liquid detergent containing a softening agent was added to the washing machine. The washing machine controls were established to provide a warm water wash (35° C.) and a cold water rinse. The duration of the wash cycle of the particular washing machine employed was about fourteen minutes. At the end of the cycle of the washing machine, the bundle was dried in a dryer for about one hour. Each bundle was exposed to three complete cycles including washing and drying. The bundles were then equilibrated and tested after the first and third cycle to measure softness as indicated in Example V. 
     The results of the softness test are set forth in Tables I and II hereinbelow. In addition to the silicone softening agents of the present invention, there was also tested organic softening agents of the prior art for comparative purposes. One softening agent was a commercially employed cationic organic fabric softening agent and a product of Sherex Chemical Company, Dublin, Ohio. The organic softening agent was monohydrogenated tallow trimethylammonium chloride available as a fifty percent by weight active material in isopropanol solvent. This organic softening agent is marketed under the trademark ADOGEN® 441. The other cationic organic softening agent tested for comparative purposes was ADOGEN® 442, also a product and trademark of Sherex, and a dihydrogenated tallow dimethylammonium chloride available as a seventy-five percent by weight active material in isopropanol solvent. Both of the comparative organic softening agents were not employed in the same amount of treat the fabric bundles as the silicone softening agents of the present invention. 
     
                       TABLE I                                                     
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              AVERAGE SOFTNESS RANK                                       
SOFTENING AGENT FIRST       THIRD                                         
IN DETERGENT*   TREATMENT   TREATMENT                                     
______________________________________                                    
(First Series)                                                            
2% Silicone of Example I                                                  
                4.0         4.1                                           
4% ADOGEN ® 441                                                       
                1.2         1.6                                           
Control**       3.5         3.5                                           
(Second Series)                                                           
2% Silicone of Example I                                                  
                5.6         4.6                                           
2% ADOGEN ® 442                                                       
                2.3         3.5                                           
Control**       2.0         1.2                                           
______________________________________                                    
 **= Liquid detergent containing 13 weight percent each of anionic and    
 nonionic surfactants; 5 weight percent ethanol; and 69 weight percent    
 water.                                                                   
 *= Water content reduced to accommodate softening agent.                 
 
    
     Table I indicates that the silicone provides a significantly higher average softness ranking in comparison to the Control and the corresponding organic softening compositions. In fact, in the &#34;First Series&#34; as shown in the Table, the cationic organic softening agent provided a softening effect less than the Control. This is due to the incompatibility between the cationic organic softening agent and the anionic surfactant present in the detergent. This incompatibility was not noted for the silicone however. Thus, in a typical wash cycle softening detergent, an anionic surfactant is required for cleaning. Where softening is a requirement in the wash cycle, a cationic organic surfactant or silicone must be added. In the past, this has proved to be a problem as the anionic and cationic surfactants complex and produce poorer cleaning as well as poorer softening. With the silicone as shown in the Table, this did not prove to be a problem however. In the case of rinse cycle softening, it is common to include cationic surfactants in order to obtain softening benefits. These benefits are often improved by incorporating a silicone in addition to the cationic surfactant. The presence in the rinse cycle of an anionic surfactant is not required as no cleaning is necessary. In fact, it has been previously believed that the presence in the rinse cycle of an anionic surfactant would decrease softening because of complexing with the cationic surfactant as noted. Contrary to this belief, however, and as shown in the &#34;Second Series&#34; in the Table, the combination of the silicone with the anionic surfactant not only did not decrease the softening benefits, but actually caused the softening to improve in comparison to the corresponding organic softening material. This is significant and provides unique and unexpected properties of the softening composition of the present invention including the silicone in combination with an anionic surfactant. 
     Comparable results were achieved using the alkanolamino functional siloxanes of the present invention as can be seen in Table II below. 
     
                       TABLE II                                                    
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              AVERAGE SOFTNESS RANK                                       
SOFTENING AGENT FIRST       THIRD                                         
IN DETERGENT*   TREATMENT   TREATMENT                                     
______________________________________                                    
(First Series)                                                            
2% Silicone (I) 4.7         3.5                                           
2% Silicone (II)                                                          
                3.7         4.0                                           
2% Silicone (III)                                                         
                3.6         4.5                                           
4% ADOGEN ® 441                                                       
                1.2         1.6                                           
Control**       3.5         3.5                                           
(Second Series)                                                           
2% Silicone (I) 3.4         3.2                                           
2% Silicone (II)                                                          
                5.3         4.7                                           
2% Silicone (III)                                                         
                2.6         4.6                                           
2% ADOGEN ® 442                                                       
                2.3         3.5                                           
Control**       2.0         1.2                                           
______________________________________                                    
 **= Liquid detergent containing 13 weight percent each of anionic and    
 nonionic surfactants; 5 weight percent ethanol; and 69 weight percent    
 water.                                                                   
 *= Water content reduced to accommodate softening agent.                 
 
    
     This application is related to copending U.S. application Ser. No. 07/460,794, filed Jan. 4, 1990, entitled &#34;Quaternary Ammonium Functional Siloxanes&#34;, and which is assigned to the same assignee as the present application. 
     It will be apparent from the foregoing that many other variations and modifications may be made in the compounds, compositions, and methods described herein without departing substantially from the essential features and concepts of the present invention. Accordingly, it should be clearly understood that the forms of the invention described herein are exemplary only and are not intended as limitations on the scope of the present invention.